Earth is often struck by solar eruptions with larger solar storms causing aurora, and in very rare cases, power outages. However, these events are nothing compared to the devastating destruction Earth would face if struck by a superflare.

These eruptions comprise of energetic particles that are flung into space from the sun. As these energetic particles head toward Earth they encounter our magnetic field that sits around our planet.

It’s then, while interacting with Earth’s magnetic field, that they cause the light display we call auroras, as beautiful as phenomena may be; it is also a reminder that our closest star is an unpredictable and dangerous neighbor.

Superflares

When our sun has large solar eruptions it pours out gigantic amounts of hot plasma, which can have major consequences for us here on Earth. However, a large solar eruption is nothing when you compare it to some stars who have what is known as “superflares.”

Since the Kepler mission discovered superflares four years ago, they have remained somewhat of a mystery. But now, an international research team led by Christoffer Karoff from Aarhus University, Denmark, has shown that this scenario is a real possibility for Earth.

The team’s work was published in Nature, and gives an insight into just how capable our sun is of producing superflares. We have suffered from large eruptions before that brought down radio communication and power supplies. The largest detected eruption took place on September 1, 1859, when astronomers observed a dark spot on the surface of the sun suddenly light up intensely over the solar surface.

This had never been observed before, and nobody knew what was to come. The following morning the first particles from this massive eruption reached Earth.

The 1859 solar storm was known as the “Carrington Event.” The auroras that came with this event could be seen as far south as Cuba and Hawaii; telegraph systems across the world were affected, and ice core records from Greenland have also indicated that Earth’s protective ozone layer was damaged by the energetic particles.

However, observations of eruptions on other stars have revealed that they can be up to 10,000 times larger than the Carrington event.

According to Aarhus University, solar flares occur when large magnetic fields on the surface of the sun collapse. When that happens, huge amounts of magnetic energy are released. Christoffer Karoff and his team have used observations of magnetic fields on the surface of almost 100,000 stars made with the new Guo Shou Jing telescope in China to show that these superflares are likely formed via the same mechanism as solar flares.

Christoffer Karoff explained:

“The magnetic fields on the surfaces of stars with superflares are generally stronger than the magnetic fields on the surface of the sun. This is exactly what we would expect if superflares are formed in the same way as solar flares.”

Not likely the sun would create a superflare

In the study, published in Nature Communications, the authors write that it’s unlikely that the sun would create a superflare, as its magnetic field is too weak. However, the authors were quick to point out that around 10 percent of the stars with superflares “had a magnetic field with strength similar to, or weaker than, the sun’s magnetic field.”

So, even though it seems not very likely, it is still possible that our sun could produce a superflare. Karoff said in a statement:

“We certainly did not expect to find superflare stars with magnetic fields as weak as the magnetic fields on the sun. This opens the possibility that the sun could generate a superflare — a very frightening thought.”

If our sun was to have a superflare that hit Earth in the near future, it would come with dire consequences. It would not just destroy all electronic equipment, but could also affect our atmosphere, and possibly destroy the planet’s ability to support life.

Evidence of superflares hidden in trees

Tree rings that date back to A.D. 775 show that there were large amounts of the radioactive isotope 14C in Earth’s atmosphere at the time. 14C forms when cosmic ray particles enter Earth’s atmosphere. These can originate from the Milky Way; however, it can also come from energetic protons cast from the sun in connection with a large solar eruption.

Observations from the Guo Shou Jing telescope

The studies from the Guo Shou Jing telescope also support the idea that the event in A.D. 775 was a small superflare (a solar eruption 10 to 100 times larger than the largest solar eruption observed during the space age), the authors of the study wrote, with Karoff saying:

“One of the strengths of our study is that we can show how astronomical observations of superflares agree with Earth-based studies of radioactive isotopes in tree rings.”

The observations from the Guo Shou Jing telescope can be used to assess how often a star with a magnetic field comparable to our sun would experience a superflare.

The study also indicates that the sun should experience a small superflare every millennium. This would prove that the event in A.D. 775 and a similar occurrence that happened in A.D. 993 were caused by small superflares on the sun.

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